In osrfNewHash(): specify a size for the osrfList used as a hash table,

In osrfNewHash(): specify a size for the osrfList used as a hash table,
so as to avoid wasting memory.

In osrfHashSet(): rearranged the logic a bit for clarity; no change in
behavior.

In osrfHashIteratorNext(): added a bit of protection against a corrupted
iterator.

Throughout: added Doxygen-style comments for documentation.  Removed
some comments from the header so that they wouldn't override more
complete comments from the implementation file.

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1775 9efc2488-bf62-4759-914b-345cdb29e865